JP3640545B2 - Method for producing positive electrode active material lithium nickelate for non-aqueous secondary battery - Google Patents

Description

【００９０】
さらに、これらの沈澱物を焼成する。そして、それぞれの焼成物を活物質に用いて電極を作製し、それらの電極の評価を行った。電極の作製及び評価は実施例１〜３と同様の方法で行った。充放電１サイクル目の放電容量（mAh/g）を表２に示す。
【００９１】
【表２】

【００９２】
表１、２の結果より、沈澱物を濾過した際に排出される濾液を繰り返し利用して沈澱物を得ることで、沈澱物中のリチウム／ニッケル比の制御が容易になり、沈澱物の均一性が向上する。さらに、この沈澱物を焼成したＬiＮiＯ₂を活物質として電極に用いた時の初期電極特性は大幅に改善される。
【００９３】
＜実施例４＞
酢酸リチウムと酢酸をモル比で１：１となるようにそれぞれ水に溶解させ、緩衝溶液を作製する。この緩衝溶液に水酸化リチウム無水物０．０３モルと、酢酸ニッケル・４水和物０．０３モルをそれぞれ溶解させる。この水溶液に粉末の蓚酸を添加して、室温で２時間撹拌する。蓚酸の添加量は０．０４５モルとする。
【００９４】
蓚酸添加により生成した沈澱物を濾過する。濾過の際に得られる濾液に酢酸カルシウムを添加し、溶液中に存在している蓚酸イオンを蓚酸カルシウムとして沈澱させ、この沈澱物を濾過により除去する。さらに、濾液に含まれる過剰の酢酸を蒸留により分離し、酢酸及びリチウムイオン濃度を加味して溶液調製を行い、この溶液に酢酸リチウム０．０３モルと酢酸ニッケル・４水和物０．０３モルを溶解させる。これに粉末の蓚酸を添加して、室温で２時間撹拌する。得られた沈澱物を濾過乾燥させ、７００℃、酸素雰囲気で１０時間焼成する。この焼成物を粉砕する。これを実施例４とする。
【００９５】
電極の作製及び評価は上述した実施例１〜３の方法に準じて行う。その結果、１回目の放電容量は１７５mAh/gであった。
【００９６】
次に、実施例４で用いた緩衝溶液を３つ用意し、これらの緩衝溶液のそれぞれから実施例４と同様にして沈澱物を得た。得られた３種の沈澱物中のリチウムとニッケルのモル比をＩＣＰ発光分析を用いて行った。その結果、これらの沈澱物中のリチウム／ニッケル比は、それぞれ１．０５、１．０４、１．０４であった。
【００９７】
さらに、得られた沈澱物を焼成する。それぞれの焼成物を用いて電極を作製し、それらの電極の評価を行った。電極の作製及び評価は実施例１〜３と同様の方法で行った。その結果、１回目の放電容量は、それぞれ１７６mAh/g、１７６mAh/g、１７５mAh/gであった。
【００９８】
以上の結果より、濾液を繰り返し用いる際に、酢酸及びリチウムイオン濃度の精度を高めるように溶液を調製した実施例４のＬiＮiＯ₂の製造方法では、得られる沈澱物中のリチウム／ニッケル比のバラツキが小さくなり、より混合状態の均一な前駆体が得られる。また、これらの前駆体を焼成したＬiＮiＯ₂は、優れた初期電極特性を与える活物質であることが認められる。
【００９９】
＜実施例５〜１０、比較例５〜７＞
酢酸リチウムと酢酸をモル比が１：１となるようにそれぞれ水に溶解させ、緩衝溶液を作製する。この緩衝溶液に水酸化リチウム無水物０．３モルと酢酸ニッケル・４水和物０．３モルを溶解させる。この水溶液に粉末の蓚酸を添加し、室温で２時間撹拌する。蓚酸の添加量は０．４５モルとする。
【０１００】
蓚酸添加により生成した沈澱物を濾過した後、濾液に酢酸リチウムを０．３モルと酢酸ニッケル・４水和物０．３モルを溶解させ、溶液を調製する。この水溶液に粉末の蓚酸０．４５モルを添加し、室温で２時間撹拌する。蓚酸の添加により沈澱物が生成した水溶液を濾過し、得られた沈澱物を乾燥させる。ここでは、焼成温度と焼成物であるＬiＮiＯ₂を用いて作製した電極の性能との関係を調べるため、様々な温度で焼成を行う。
【０１０１】
即ち、６００℃、６５０℃、７００℃、７５０℃、８００℃、８５０℃、９００℃、９４０℃、９８０℃の各温度にて沈澱物を焼成する。焼成時間はいずれも５時間とする。また、いずれも酸素雰囲気で焼成する。このときのそれぞれを、比較例５、実施例５〜１０、比較例６、７とする。
【０１０２】
上記の製造方法により得られたＬiＮiＯ₂を活物質に用いて電極を作製する。このとき、ＬiＮiＯ₂、導電材になるアセチレンブラック、及び結着材になるポリテトラフルオロエチレンを１００：８：１０の割合で混合する他は、電極作製の手順やペレットの重量及びサイズ等、上述した実施例１〜３の電極作製方法に準ずる。
【０１０３】
また、電解液としてエチレンカーボネート、ジエチルカーボネートを体積比１：１の割合で混合した溶媒に、過塩素酸リチウムを１Ｍの割合で溶解したものを用いる他は、上述した実施例１〜３の電極評価方法に準ずる。
【０１０４】
図２は、焼成温度と１回目の放電容量との関係を示した図である。沈澱物を濾過した後の溶液を用いて再び沈澱物を得て、焼成することによりＬiＮiＯ₂を製造した場合でも、良好な初期電極特性を与えることがわかる。また、焼成温度が６５０℃〜９００℃、好ましくは７００℃〜８５０℃であれば、高い値の放電容量が得られている。従って、焼成温度を６５０℃〜９００℃とすることを特徴とした、本発明に係るＬiＮiＯ₂の製造方法を用いれば、初期電極特性の良好な電極を得ることが認められた。
【０１０５】
＜実施例１１〜１６、比較例８〜１０＞
酢酸リチウムと酢酸をモル比が１：１になるようにそれぞれ水に溶解させ、緩衝溶液を作製する。この緩衝溶液に水酸化リチウム無水物０．３モルと酢酸ニッケル・４水和物０．２４モル及び酢酸コバルト０．０６モルをそれぞれ溶解させる。この水溶液に粉末の蓚酸を添加し、室温で２時間撹拌する。蓚酸の添加量は０．４５モルとする。
【０１０６】
蓚酸添加により生成した沈澱物を濾過した後、濾液に酢酸リチウム０．３モルと酢酸ニッケル０．２４モル及び酢酸コバルト０．０６モルをそれぞれ溶解させ、溶液を調製する。この水溶液に粉末の蓚酸０．４５モルを添加し、室温で２時間撹拌する。蓚酸の添加により沈澱物が生成した水溶液を濾過し、得られた沈澱物を乾燥させる。ここでは、焼成温度と焼成物であるＬiＮi_0.8Ｃo_0.2Ｏ₂を用いて作製した電極の性能との関係を調べるため、様々な温度で焼成を行う。
【０１０７】
即ち、６００℃、６５０℃、７００℃、７５０℃、８００℃、８５０℃、９００℃、９４０℃、９８０℃の各温度にて沈澱物を焼成する。焼成時間はいずれも５時間とする。また、いずれも酸素雰囲気で焼成する。このときのそれぞれを、比較例８、実施例１１〜１６、比較例９、１０とする。
【０１０８】
上記の製造方法により得られたＬiＮi_0.8Ｃo_0.2Ｏ₂を活物質に用いて電極を作製する。このとき、ＬiＮi_0.8Ｃo_0.2Ｏ₂、導電材になるアセチレンブラック、及び結着材になるポリテトラフルオロエチレンを１００：８：１０の割合で混合する他は、電極作製の手順やペレットの重量及びサイズ等、上述した実施例１〜３の電極作製方法に準ずる。
【０１０９】
また、電解液としてエチレンカーボネート、ジエチルカーボネートを体積比１：１の割合で混合した溶媒に、過塩素酸リチウムを１Ｍの割合で溶解したものを用いる他は、上述した実施例１〜３の電極評価方法に準ずる。
【０１１０】
図３は、焼成温度と１回目の放電容量との関係を示した図である。沈澱物を濾過した後の溶液を用いて再び沈澱物を得て、焼成することによりＬiＮi_0.8Ｃo_0.2Ｏ₂を製造した場合でも、良好な初期電極特性を与えることがわかる。また、焼成温度が６５０℃〜９００℃、好ましくは７００℃〜８５０℃であれば、高い値の放電容量が得られている。従って、焼成温度を６５０℃〜９００℃とすることを特徴とした、本発明に係るＬiＮi_0.8Ｃo_0.2Ｏ₂の製造方法を用いれば、初期放電容量の高い電極を得ることが認められた。
【０１１１】
＜実施例１７〜２２、比較例１１〜１８＞
酢酸リチウムと酢酸をモル比が１：１となるようにそれぞれ０．３モルずつ水に溶解させ、緩衝溶液を作製する。この緩衝溶液に水酸化リチウム無水物０．３モルと酢酸ニッケル・４水和物０．３モルを溶解させる。この水溶液に粉末の蓚酸を添加し、室温で２時間撹拌する。蓚酸の添加量は０．４５モルとする。
【０１１２】
蓚酸添加により生成した沈澱物を濾過し、得られた沈澱物を乾燥させる。ここでは、焼成雰囲気における酸素の体積割合と、生成したＬiＮiＯ₂を用いて作製した電極の放電容量との関係を調べるため、様々な酸素濃度の雰囲気で焼成を行う。
【０１１３】
即ち、酸素と窒素の混合気体において、酸素の体積割合が１０％、２０％（空気中）、３０％、５０％、７０％、８０％、１００％の各雰囲気で沈澱物を焼成する。ただし、いずれの場合も７００℃で８時間焼成する。得られた焼成物を粉砕する。このときのそれぞれを、比較例１１〜１７とする。
【０１１４】
沈澱物を濾過した際に得られる溶液を上述した実施例４と同様に調製した後、酢酸リチウム０．３モルと酢酸ニッケル０．３モルを溶解させる。これに粉末の蓚酸０．４５モルを添加して、室温で２時間撹拌する。生成した沈澱物を濾過乾燥し、上述した様々な酸素濃度の雰囲気で焼成する。
【０１１５】
即ち、酸素の体積割合が１０％、２０％（空気中）、３０％、５０％、７０％、８０％、１００％の各雰囲気で沈澱物を焼成する。ただし、いずれの場合も７００℃で８時間焼成する。得られた焼成物を粉砕する。このときのそれぞれを、比較例１８、実施例１７〜２２とする。
【０１１６】
上記のＬiＮiＯ₂製造法により得られたＬiＮiＯ₂を活物質に用いて、電極を作製する。このとき、ＬiＮiＯ₂、導電材になるアセチレンブラック、及び結着材になるポリテトラフルオロエチレンを１００：１５：８の割合で混合する他は、電極作製の手順やペレットの重量及びサイズ等、上述した実施例１〜３の電極作製方法に準ずる。
【０１１７】
また、電解液としてプロピレンカーボネート、ジメチルカーボネートを体積比１：１の割合で混合した溶媒に、リンフッ化リチウムを１Ｍの割合で溶解したものを用いる他は、上述した実施例１〜３の電極評価方法に準ずる。
【０１１８】
図４は、焼成雰囲気の酸素濃度と充放電１回目の放電容量との関係を示した図である。図４より、沈澱物を濾過した後の溶液を用いて再び沈澱物を得て、焼成することによりＬiＮiＯ₂を製造した場合でも、良好な初期電極特性を与えることがわかる。また、酸素濃度が２０％以上、好ましくは５０％以上、特に８０％以上であれば、高い値の放電容量が得られている。従って、焼成雰囲気における酸素の体積割合を２０％以上とすることを特徴とした、本発明に係るＬiＮiＯ₂の製造方法を用いれば、初期電極特性の良好な電極を得ることが認められた。
【０１１９】
＜実施例２３＞
本実施例では、本発明に係るＬiＮiＯ₂の製造方法により製造したＬiＮiＯ₂を正極活物質として簡単な電池を作製して、充放電試験を行う。実施例２で述べた正極の作製方法に準じて正極を作製し、直径１５mm、重量５０mgのペレットとする。
【０１２０】
負極活物質には熱分解炭素（（００２）面と平行な隣接面との面間隔（ｄ００２）：０．３３７nm、（００２）面方向の結晶子の厚さ（Ｌｃ）：１５nm、アルゴンレーザーラマン法による散乱スペクトルの１５８０cm^-1付近のピークに対する１３６０cm^-1付近のピークの強度比（Ｒ値）：０．４５）を用いる。
【０１２１】
プロパンを出発原料に用いて７５０℃で２時間常圧気相熱分解させ、ニッケルメッシュ（表面積４cm²）の基板に堆積させる。これにニッケル線をスポット溶接して集電を取り、水分除去のために２００℃で減圧乾燥させたものを負極（重量３５mg）とする。
【０１２２】
ビーカー型セルにプロピレンカーボネートとジエチルカーボネートを体積比１：１で混合した溶媒に過塩素酸リチウムを１Ｍの割合で溶解させた電解液を入れ、この電解液に上述した正極及び負極を浸す。
【０１２３】
この電池の充放電試験は次の通りに行う。０．２mAで上限電圧４．４Ｖまで定電流充電を行い、続いて同じ電流で２．５Ｖまで定電流放電を行った。２回目以降も同様に行う。その結果、充放電１サイクル目の放電容量は７．９mAh、１００サイクル目の放電容量は７．１mAhであった。
【０１２４】
＜実施例２４＞
本実施例では、本発明に係るコイン型電池の充放電試験を行う。実施例２で述べたＬiＮiＯ₂の製造方法により得られたＬiＮiＯ₂を活物質に用いて、正極を作製し、直径１５mm、厚さ０．７５mm、重量０．２０ｇのペレットとする。
【０１２５】
負極の作製方法は次の通りである。負極活物質にはマダガスカル産の天然黒鉛（鱗片状、粒径：１１μｍ、（００２）面と平行な隣接面との面間隔（ｄ００２）：０．３３７nm、（００２）面方向にある結晶子の厚さ（Ｌｃ）：２７nm、（００２）面方向にある結晶層の拡がり（Ｌa）：１７nm、アルゴンレーザーラマン法による散乱スペクトルの１５８０cm^-1付近のピークに対する１３６０cm^-1付近のピークの強度比（Ｒ値）：０、比表面積：８m²/g）を用いる。
【０１２６】
天然黒鉛と結着材となるポリテトラフルオロエチレンを、１０：１の割合で混合する。この混合物に集電体としてニッケルメッシュを加え、加圧成形して直径１５mm、厚さ０．５９mm、重量０．１ｇのペレットを作製する。このペレットを水分除去のために２００℃、減圧下で乾燥させる。
【０１２７】
これらの電極を用いたコイン型電池の構成は次の通りである。図５は本発明に係るコイン型電池の断面を示している。低い円筒形の正極缶１の内部に、側面に沿って絶縁パッキン８が載置されている。また、この絶縁パッキン８より中心側に正極集電体２と一体となった正極３が圧着されている。
【０１２８】
このとき、正極集電体２は正極缶１の底面に接している。この正極３の上にポリプロピレン不織布のセパレータ７と負極集電体５と一体となっている負極６が、この順に下から上へ互いに密接して配置されている。セパレータ７には、エチレンカーボネートとジエチルカーボネートを体積比１：１で混合した溶媒に、リンフッ化リチウムを１Ｍの割合で溶解させた電解液が含浸している。
【０１２９】
負極６の上には負極缶４か重ねられており、この負極缶４と正極缶１は絶縁パッキン８を介在させて、かしめで密封されている。これによって、負極６は負極缶４に圧着しており、特に負極集電体５は負極缶４の内面に接している。
【０１３０】
このコイン型電池の充放電試験は次の通りに行う。充放電電流は１mAとし、初めに充電上限電圧４．４Ｖまで定電流充電を行い、続いて放電下限電圧２．５Ｖまで定電流放電を行う。２回目以降も同じ電流、電圧の範囲で充放電を繰り返す。
【０１３１】
その結果、充放電１サイクル目の放電容量は２８．５mAh、１００サイクル目の放電容量は２５．０mAhであった。
【０１３２】
＜実施例２５＞
本実施例では、本発明に係る円筒形電池の充放電試験を行う。まず、シート状の正極を作製する。実施例２で述べたＬiＮiＯ₂の製造方法により正極活物質ＬiＮiＯ₂を製造する。
【０１３３】
このＬiＮiＯ₂を活物質に用いた電極の作製方法は次の通りである。ＬiＮiＯ₂、導電材となるアセチレンブラック、及び結着材となるポリフッ化ビニリデンを１００：７：１０の割合で混合する。ここに、分散剤としてＮ−メチル−２−ピロリドンを加えてさらに混合し、正極ペーストとする。
【０１３４】
この正極ペーストを集電体となるアルミニウム箔（厚さ２０μｍ）の両面に塗布し、乾燥させた後、圧延して短冊状に切断する。この正極における単位面積あたりの活物質の重量は４０mg/cm²となった。また、この正極の一端に正極リードとなるアルミニウムタブを、スポット溶接にて取り付ける。
【０１３５】
負極活物質に人造黒鉛（粒径：８μｍ、（００２）面の平行する隣接面との面間隔（ｄ００２）：０．３３７nm、（００２）面方向にある結晶層の厚さ（Ｌｃ）：２５nm、（００２）面方向にある結晶層の拡がり（Ｌa）：１３nm、アルゴンレーザーラマン法による散乱スペクトルの波数が１５８０cm^-1付近のピークに対する１３６０cm^-1付近のピークの強度比（Ｒ値）：０、比表面積：１２m²/g）を用いる。この人造黒鉛と結着材となるポリフッ化ビニリデンを、１００：１０の割合で混合する。
【０１３６】
この混合物に、分散剤としてＮ−メチル−２−ピロリドンを加えてさらに混合し、負極ペーストとする。負極ペーストを集電体となる銅箔（厚さ１８μｍ）の両面に塗布し、乾燥させた後、圧延し、短冊状に切断する。この負極における活物質の単位面積あたりの重量は２０mg/cm²となった。また、この負極の一端に負極リードとなるニッケルタブを、スポット溶接にて取り付ける。
【０１３７】
これらの電極を用いた円筒形電池の構成は次の通りである。図６は本発明に係る円筒形電池の断面を示している。尚、この図において、正極蓋１１、絶縁パッキン１２及びセパレータ１４には断面を示すハッチングを省略している。正極１６、負極１５各１枚ずつの間にポリエチレン製微多孔質のセパレータ１４が挟まれている。これらを対向するように端からスパイラル状に巻回し、円筒形の巻回要素を形成する。
【０１３８】
この円筒形巻回要素は上面から正極リード、下面から負極リードがそれぞれ引き出された状態で、円筒形の電池缶（直径１７mm、高さ５０mm、ステンレス製）内に収納されている。そして、正極リードは安全弁付き正極蓋に、負極リードは電池缶の底面にスポット溶接によってそれぞれ取り付けられている。また、巻回要素の中心部には、巻き崩れ防止のためにセンターピン１７（直径３．４mm、長さ４０mm、ステンレス製チューブ）が挿入されている。
【０１３９】
電解質として、エチレンカーボネートとジエチルカーボネートを体積比１：１で混合した混合溶媒に、リンフッ化リチウムを１Ｍの割合で溶解させた電解液が、電池缶に注液されている。また、正極蓋１１と電池缶１３は絶縁パッキン１２を介在させて、かしめで密封されている。
【０１４０】
この円筒形電池の充放電試験は次の通りに行う。２５℃の恒温槽において、５００mA、上限電圧４．２Ｖの定電流定電圧充電を３時間行い、１００mA、下限電圧２．７５Ｖの定電流放電を行った。２回目以降も同様に行う。その結果、充放電１サイクル目の放電容量は９１８mAh、５０サイクル目の放電容量は８０５mAhであった。従って、本発明に係る非水系二次電池は繰り返される充放電にも、放電容量が減少しない二次電池であることが認められた。
【０１４１】
【発明の効果】
以上説明したように、ニッケル化合物とリチウム化合物を原料とし、これを緩衝溶液中に溶解させた後、蓚酸を加えて共沈させ、沈澱物を濾過した際に排出される濾液を緩衝溶液として再び用いて繰り返し前駆体を得るようにしたことを特徴とする本発明に係るＬiＮiＯ₂の製造方法によると、リチウムとニッケルのモル比（リチウム／ニッケル）のバラツキが少ないより均一な前駆体が得られる。
【０１４２】
また、沈澱物を濾過した際に得られる濾液から蓚酸イオン及び酢酸を分離した後、溶液中の酢酸及びリチウムイオン濃度の精度を高めるように溶液を調製することで、更に前駆体の均一性は安定する。
【０１４３】
また、蓚酸を添加する前の条件に再度調製することにより、濾液を繰り返し用いてＬiＮiＯ₂の前駆体を得るようにしているので、原材料を毎回大量に用いる必要がなくなりコストの削減がはかれるとともに、資源の有効利用が可能となる。
【０１４４】
この前駆体を焼成して得られるＬiＮiＯ₂を活物質として電極に用いた、本発明に係る非水系二次電池では、高い値の初期放電容量を得ることができる。さらに、本発明に係る二次電池では、繰り返される充放電にも放電容量があまり減少しないので、寿命の長い二次電池となる。
【図面の簡単な説明】
【図１】 本発明に係るＬiＮiＯ₂又はＬiＮi_1-XＭ_XＯ₂（0＜Ｘ＜0.5、Ｍは遷移金属又は３Ｂ族元素又は４Ｂ族元素又は５Ｂ族元素から選ばれる少なくとも１種の元素）の製造方法を示した図である。
【図２】 実施例５〜１０、比較例５〜７の焼成温度と初回放電容量との関係を示した図である。
【図３】 実施例１１〜１６、比較例８〜１０の焼成温度と初回放電容量との関係を示した図である。
【図４】 実施例１７〜２２、比較例１１〜１８の焼成雰囲気の酸素濃度と初回放電容量との関係を示した図である。
【図５】 本発明に係るコイン型電池の断面を示した図である。
【図６】 本発明に係る円筒形電池の断面を示した図である。
【符号の説明】
１ 正極缶
２ 正極集電体
３ 正極
４ 負極缶
５ 負極集電体
６ 負極
７ セパレータ
８ 絶縁パッキン
１１ 正極蓋
１２ 絶縁パッキン
１３ 電池缶
１４ セパレータ
１５ 負極
１６ 正極
１７ センターピン[0001]
BACKGROUND OF THE INVENTION
The present invention is LiNiO ₂ Or LiNi _1-X M _X O ₂ (0 <X <0.5, M is at least one element selected from a transition metal, a group 3B element, a group 4B element, or a group 5B element) and its LiNiO ₂ Or LiNi _1-X M _X O ₂ The present invention relates to a non-aqueous secondary battery using as a positive electrode active material (0 <X <0.5, M is at least one element selected from transition metals or 3B, 4B, and 5B group elements).
[0002]
[Prior art]
Conventional lithium nickelate (LiNiO ₂ There are the following reports as typical production methods.
[0003]
LiNiO as shown in Journal of the American Chemical Society, J. Am. Chem. Soc., 76, 1499 (1954) ₂ In an example of the manufacturing method, solid anhydrous lithium hydroxide and metallic nickel are mixed and fired in an air atmosphere.
[0004]
In addition, LiNiO disclosed in JP-A-2-40861 ₂ In an example of the production method, solid nickel hydroxide monohydrate and solid nickel oxide are mixed. First, the mixture is fired at 600 ° C. in an air atmosphere. Then, the fired product is pulverized and fired again at 600 ° C. to 800 ° C.
[0005]
Further, LiNiO disclosed in Japanese Patent Laid-Open No. 5-205741 ₂ In an example of the manufacturing method, solid lithium peroxide and nickel oxide are mixed, fired at 750 ° C. or lower, and then rapidly cooled.
[0006]
Further, LiNiO shown in Japanese Patent Laid-Open No. 5-251079. ₂ In an example of the production method, solid lithium nitrate and at least one of solid nickel hydroxide and nickel oxyhydroxide are mixed and fired at 500 ° C to 1000 ° C.
[0007]
In addition, LiNiO disclosed in JP-A-6-203834 ₂ In an example of the production method, nickel acetate and lithium acetate are dissolved by heating in ethylene glycol, and the heated and solidified material is heat treated and ground in air at 400 ° C. and then fired at 700 ° C. in an oxygen stream. The fired product is fired again at 800 ° C. in an oxygen stream.
[0008]
Also, LiNiO shown in Chemistry Express, 6, 161 (1991). ₂ In an example of the production method, an equimolar mixture of a 4.5 M lithium hydroxide aqueous solution and a 1.0 M nickel nitrate aqueous solution at 60 ° C. The mixed solution is evaporated to dryness under stirring under reduced pressure, and the resulting solid material is pulverized, pre-fired at 300 ° C., and fired again at 800 ° C.
[0009]
In addition, in the example of the method for producing a composite oxide of lithium and nickel disclosed in JP-A-6-44970, at least one selected from nickel halide, nickel sulfate, nickel phosphate, nickel acetate, and nickel oxalate. A saturated aqueous solution of at least one lithium salt selected from lithium hydroxide, lithium carbonate, and lithium hydrogen carbonate equimolar to this nickel salt is poured into a saturated aqueous solution of nickel salt. The mixture is evaporated to dryness with stirring and mixing in air or under reduced pressure, and the obtained cake-like solid material is calcined at 600 ° C to 800 ° C.
[0010]
In addition, in an example of the method for producing a composite oxide of lithium and nickel disclosed in JP-A-6-44971, at least one selected from nickel oxide, nickel oxyhydroxide, nickel hydroxide, nickel carbonate, A saturated aqueous solution of at least one lithium salt selected from lithium halide, lithium nitrate, lithium sulfate, lithium phosphate, lithium borate, lithium acetate, and lithium oxalate is added to a water-insoluble or insoluble nickel compound powder. Add and mix thoroughly. This mixture is evaporated to dryness with stirring in air or under reduced pressure, and the obtained cake-like solid substance is calcined at 600 ° C to 800 ° C.
[0011]
In addition, LiNiO shown in JP-A-6-96769 ₂ In an example of the production method, the lithium source and the nickel source are mixed so that the ratio of the molar amount of lithium in the lithium source to the molar amount of nickel in the nickel source is 1: 1. At this time, a small amount of water is added as a dispersion medium. The mixture is dried and fired at 650 ° C to 800 ° C.
[0012]
In addition, LiNiO disclosed in JP-A-9-156931 ₂ In one example of the production method, nickel oxide powder and lithium compound of either lithium hydroxide or lithium nitrate are weighed so that the molar ratio of lithium to nickel is 1: 1. Then, the lithium compound melted at a melting temperature of the lithium compound or higher and 500 ° C. or lower is infiltrated into the nickel oxide powder and fired in the presence of oxygen or an oxygen-enriched gas.
[0013]
In the method for producing a positive electrode active material for a non-aqueous secondary battery described above, the method of mixing a lithium compound and a nickel compound in a solid state has a problem that the mixed state before firing is not uniform.
[0014]
Moreover, in the method of mixing a lithium compound and a nickel compound in the state of an aqueous solution, when the mixed aqueous solution is dried and solidified, the solubility of each solute is different, so that the solute does not precipitate at the same time. Therefore, in the obtained solid substance, the lithium compound and the nickel compound are not uniformly mixed.
[0015]
In addition, a method in which nickel acetate and lithium acetate are dissolved in ethylene glycol by heating and the solid material that has been heated and dried and solidified is fired twice is not preferable because it requires a long firing time and the manufacturing process becomes complicated. . Moreover, even in the solid material before firing obtained by this method, the mixed state of the lithium compound and the nickel compound is not sufficient.
[0016]
In addition, in a method of dispersing a nickel compound powder that is hardly soluble or insoluble in water in an aqueous lithium salt solution or a method of dispersing a lithium compound and a nickel compound in water and stirring and kneading, the solute is removed when water as a dispersion medium is removed. Therefore, the obtained substance is not a mixture of a lithium compound and a nickel compound uniformly.
[0017]
Also, even when the molten salt of the lithium compound is infiltrated into the nickel oxide powder, the mixed state of both is somewhat improved, but it is still insufficient.
[0018]
In a non-aqueous secondary battery using a fired product made of a material whose mixing state is not sufficient as the positive electrode active material, the discharge capacity is remarkably lowered with an increase in the number of charge / discharge cycles, and the electrode is rapidly deteriorated.
[0019]
In order to solve the above problems, LiNiO disclosed in JP-A-10-106564 is disclosed. ₂ In this production method, a water-soluble lithium compound and a water-soluble nickel compound are first dissolved in water to prepare an aqueous solution. Next, oxalic acid is added to the aqueous solution to coprecipitate a lithium compound and a nickel compound. The obtained precipitate is dried and then calcined.
[0020]
By this coprecipitation reaction, the lithium compound and the nickel compound in the precipitate are uniformly mixed. Therefore, LiNiO obtained by firing this ₂ The non-aqueous secondary battery using the positive electrode active material has improved charge / discharge cycle characteristics.
[0021]
[Problems to be solved by the invention]
However, LiNiO disclosed in the above-mentioned JP-A-10-106564 ₂ In this production method, since lithium and nickel are precipitated as a composite oxalate, a precursor in which a lithium compound and a nickel compound are uniformly mixed is obtained, but lithium oxalate is relatively easy to dissolve in water. Every time the precursor was produced, the molar ratio of lithium and nickel in the precursor (lithium / nickel) varied, and reproducibility was not sufficient.
[0022]
In addition, in the step of preparing an aqueous solution of a lithium compound and a nickel compound before adding oxalic acid, the lithium compound as a raw material must be added several times to ten times in a molar ratio of lithium to nickel with respect to the nickel compound. It was.
[0023]
Therefore, LiNiO obtained by firing the precursor produced by this coprecipitation reaction ₂ The non-aqueous secondary battery using a positive electrode active material has improved initial discharge capacity and good charge / discharge cycle characteristics, but has a problem that a stable active material cannot be obtained and in terms of raw material costs. There was a problem that it was costly and a problem that there was a lot of waste in terms of resources.
[0024]
The present invention relates to a positive electrode active material LiNiO for a non-aqueous secondary battery that exhibits stable charge / discharge characteristics. ₂ It is an object of the present invention to provide a method for producing a battery at low cost without waste, and to provide a lithium ion secondary battery having good charge / discharge cycle characteristics.
[0025]
[Means for Solving the Problems]
To achieve the above object, the LiNiO of claim 1. ₂ The method for producing a positive electrode active material for a non-aqueous secondary battery comprising Lithium acetate or lithium hydroxide When Nickel acetate The vinegar Acid and Lithium acetate An aqueous solution is prepared by dissolving in a buffer solution consisting of Next, oxalic acid is added to the aqueous solution to form a precipitate. The formed precipitate is separated from the aqueous solution by filtration, centrifugation or the like. The obtained precipitate is dried and then calcined. And the precipitate was filtered Each cation added by adding any one compound of acetate, oxide, and hydroxide containing cation that is difficult to dissolve in water, using oxalate ions remaining in the solution as oxalate from the solution discharged at the time As an oxalate containing Next, acetic acid is separated by distillation, extraction, etc., and the solution is prepared again under the conditions before adding succinic acid. The filtrate Repeated use The
[0031]
Claims 2 LiNi _1-X M _X O ₂ (0 <X <0.5, M is at least one element selected from a transition metal, a group 3B element, a group 4B element, or a group 5B element) Lithium acetate or lithium hydroxide When Nickel acetate And a compound containing at least one element selected from transition metals, 3B group elements, 4B group elements, and 5B group elements vinegar Acid and Lithium acetate An aqueous solution is prepared by dissolving in a buffer solution consisting of Next, oxalic acid is added to the aqueous solution to form a precipitate. The formed precipitate is separated from the aqueous solution by filtration, centrifugation or the like. The obtained precipitate is dried and then calcined. Then, any one compound of acetate, oxide, and hydroxide containing a cation that is difficult to dissolve in water, using oxalate ions remaining in the solution as oxalate from the solution discharged when the precipitate is filtered. In addition, it is removed as an oxalate containing each added cation. The acetic acid is then separated by distillation, extraction, etc., and the filtrate is repeatedly used by preparing the solution again under the conditions before adding succinic acid.
[0032]
Claims 3 The invention of claim 1 Or claim 2 LiNiO ₂ -Containing positive electrode active material for non-aqueous secondary battery or LiNi _1-X M _X O ₂ In the method for producing a positive electrode active material for a non-aqueous secondary battery, wherein 0 <X <0.5, M is at least one element selected from transition metals, 3B group elements, 4B group elements or 5B group elements, As a method of removing the water, calcium acetate is added to the filtrate to precipitate as calcium oxalate.
[0033]
Claim 1 To claims 3 According to the configuration, when the filtrate is repeatedly used, the pH of the solution is taken into account, so that the accuracy of the lithium ion and acetic acid concentration in the solution is increased. Therefore, the precipitate obtained as a composite oxalate is further mixed. Becomes uniform. After the precipitate is dried, the fired fired product can be used as a positive electrode active material for a non-aqueous secondary battery having stable charge / discharge cycle characteristics. In particular, the claims 3 According to the above, since the oxalate ions contained in the filtrate are removed by adding calcium acetate, the accuracy of the pH, lithium ion, and acetic acid concentration of the solution can be further improved.
[0034]
Claims 4 The invention of claim 1 to claim 1 3 Any LiNiO ₂ -Containing positive electrode active material for non-aqueous secondary battery or LiNi _1-X M _X O ₂ (0 <X <0.5, M is at least one element selected from transition metals, 3B group elements, 4B group elements, and 5B group elements) As described above, at a temperature of 650 ° C. or higher and 900 ° C. or lower, preferably 700 ° C. or higher and 850 ° C. or lower, the volume ratio of oxygen is higher in air or in air than 21% to 100%, preferably 50% to 100%. Firing is performed in the following atmosphere. By baking under these conditions, crystallinity is improved and the remaining amount of impurities is reduced.
[0035]
Also , Lithium acetate or lithium hydroxide and nickel acetate are From the viewpoint of repeatedly using the filtrate after filtering the precipitate, it is preferable from the viewpoint that it is easy to prepare a similar composition ratio every time and that it is difficult to remain as an impurity when the precipitate is baked.
[0036]
Also , Loose Use a mixed aqueous solution of acetic acid and lithium acetate as the impact solution By This makes it possible to reduce raw material costs and effectively use resources.
[0038]
DETAILED DESCRIPTION OF THE INVENTION
LiNiO according to the present invention ₂ The manufacturing method will be described in detail. FIG. 1 shows LiNiO by the filtrate circulation process according to the present invention. ₂ It is the figure which showed this manufacturing method. First, this flowchart will be described.
[0039]
In step # 5, an aqueous solution is prepared by dissolving a water-soluble lithium compound and a water-soluble nickel compound in a buffer solution. It is preferable to use either lithium hydroxide or lithium acetate as the lithium compound in terms of repeatedly circulating the filtrate. Further, nickel acetate is preferably used as the nickel compound for the same reason. As the buffer solution, a mixed aqueous solution of acetic acid and lithium acetate or lithium hydroxide is preferably used for the same reason.
[0040]
In step # 10, the lithium compound is coprecipitated by adding oxalic acid to the aqueous solution prepared in step # 5. The lithium compound and the nickel compound in the precipitate produced by the coprecipitation reaction are in a uniformly mixed state.
[0041]
Coprecipitation can be performed by adding oxalic acid to an aqueous solution in which the lithium compound and the nickel compound are dissolved. Succinic acid may be added in the form of an aqueous solution or in a solid state. Addition with an aqueous solution is preferable because uniform fine particles are formed. This method is also preferable because the coprecipitation reaction can be easily controlled by adding it as a solid.
[0042]
The amount of succinic acid added is preferably 1.3 to 2.5 times in molar ratio with respect to nickel ions in the aqueous solution. If it is less than 1.3 times, the pH of the solution becomes difficult to control, and the precipitate is calcined to produce LiNiO. ₂ Can't get. On the other hand, when it is more than 2.5 times, LiNiO obtained by baking the precipitate. ₂ Is not preferable because it contains a large amount of impurities.
[0043]
In step # 15, the formed precipitate is filtered off by filtration, centrifugation or the like. Then, the precipitate obtained by filtration in step # 20 is dried and fired in step # 25.
[0044]
Firing is preferably performed at a temperature of 650 ° C. to 900 ° C. and in an atmosphere of 20% to 100% oxygen. In particular, in order to obtain good electrode characteristics, it is preferable to perform firing at a temperature of 700 ° C. to 850 ° C. in an atmosphere of 50% to 100% oxygen. Outside this range, there are problems such as slow growth of crystals, decomposition of crystals, and the presence of many impurities.
[0045]
Next, a filtrate circulation process in which the filtrate after filtering the precipitate is repeatedly used as a mother liquor will be described. The present invention provides two methods for this filtrate circulation process.
[0046]
In the first method, the filtrate discharged after filtering the precipitate formed in step # 15 is used again as a buffer solution. That is, the process returns to step # 5 as indicated by (1) in FIG. 1, and the precipitate is obtained again as described above. This is repeated and the filtrate is circulated.
[0047]
The second method is as follows in order to improve the accuracy of the concentration of acetic acid and lithium ions in the solution when the filtrate is repeatedly used. That is, after filtering the precipitate produced | generated by step # 15, any one compound of acetate, an oxide, and a hydroxide containing the cation which is hard to melt | dissolve in water as an oxalate in step # 30 in the discharged | emitted filtrate. The oxalate ions in the filtrate are precipitated as oxalates containing the added cations, and the oxalate precipitated in step # 35 is separated and removed by filtration.
[0048]
As the acetate added in Step # 30, magnesium acetate, calcium acetate, strontium acetate, barium acetate, aluminum diacetate hydroxide, silver acetate, cadmium acetate, cobalt acetate, copper acetate, iron acetate, lanthanum acetate, manganese acetate, Acetates such as nickel acetate, lead acetate, tin acetate, yttrium acetate and zinc acetate are preferred. Of these, acetates such as calcium acetate, aluminum hydroxide hydroxide, and nickel acetate are more preferable in terms of cost and recyclability.
[0049]
Similarly, oxides added in step # 30 include calcium oxide, silver oxide, barium oxide, cadmium oxide, cobalt oxide, copper oxide, iron oxide, gallium oxide, magnesium oxide, manganese oxide, nickel oxide, tin oxide, and oxide. There are yttrium and zinc oxide.
[0050]
Similarly, hydroxides added in Step # 30 include calcium hydroxide, strontium hydroxide, aluminum hydroxide, barium hydroxide, cadmium hydroxide, cerium hydroxide, cobalt hydroxide, copper hydroxide, iron hydroxide, Examples include gallium hydroxide, magnesium hydroxide, manganese hydroxide, nickel hydroxide, yttrium hydroxide, and zinc hydroxide.
[0051]
Further, acetic acid is separated from the filtrate obtained by filtration by distillation, extraction or the like in step # 40. The solution from which acetic acid has been separated is appropriately prepared in step # 45 and used again as a solution before addition of oxalic acid. By repeating this operation, a precursor was obtained in the same manner as described above, and this was fired to obtain uniform LiNiO. ₂ Can be manufactured.
[0052]
LiNiO by the filtrate circulation process according to the present invention described here. ₂ The manufacturing method is LiNi _1-X M _X O ₂ (0 <X <0.5, M is at least one element selected from a transition metal, a group 3B element, a group 4B element, or a group 5B element), specifically, step # of FIG. 5 is only added with the step of adding at least one element selected from the transition metal, the group 3B element, the group 4B element, or the group 5B element shown in step # 50, and detailed description thereof will be omitted.
[0053]
As the at least one element selected from a transition metal, a group 3B element, a group 4B element or a group 5B element to be added in step # 50, a surface for repeatedly circulating the filtrate when the precipitate is filtered in step # 15, and a final It is preferable to use acetate such as vanadium acetate, chromium acetate, manganese acetate, cobalt acetate, copper acetate, zinc acetate, yttrium acetate, lanthanum acetate, etc. .
[0054]
Next, LiNiO according to the present invention ₂ LiNiO obtained by the manufacturing method of ₂ A non-aqueous secondary battery using as a positive electrode active material for the positive electrode will be described. However, the method for manufacturing the non-aqueous secondary battery is not limited to this.
[0055]
The positive electrode is LiNiO ₂ In addition, the conductive material, the binding material, and, in some cases, the composite material mixed with the solid electrolyte or the like is used. As the conductive material, carbon such as carbon black, acetylene black, ketjen black, graphite powder (natural graphite, artificial graphite), metal powder, metal fiber, and the like can be used, but are not limited thereto. . As the binder, fluorine-based polymers such as polytetrafluoroethylene and polyvinylidene fluoride, polyolefin-based polymers such as polyethylene, polypropylene, and ethylene-propylene-diene-terpolymer, styrene butadiene rubber, and the like can be used. It is not limited to.
[0056]
The mixing ratio can be 1 to 50 parts by weight of the conductive material and 1 to 30 parts by weight of the binder with respect to 100 parts by weight of the active material. If the conductive material is less than 1 part by weight, the resistance or polarization of the electrode increases and the discharge capacity decreases, so that a practical secondary battery cannot be produced. If the conductive material is more than 50 parts by weight (the weight part varies depending on the type of conductive material to be mixed), the amount of the active material contained in the electrode is reduced, so that the discharge capacity as the positive electrode is reduced. Further, if the binding material is less than 1 part by weight, the determination force is lost, and if it is more than 30 parts by weight, the amount of the active material contained in the electrode is reduced as in the case of the conductive material, and further described above. As described above, the resistance or polarization of the electrode increases and the discharge capacity decreases, which is not practical.
[0057]
There are two methods for forming this mixture: compressing it into a pellet, or applying a paste with a suitable solvent added to the mixture on a current collector, drying and rolling it into a sheet. It is not limited to. The positive electrode is provided with a current collector for transferring electrons. As the current collector, a single metal, an alloy, carbon or the like is used. For example, there are titanium, aluminum, stainless steel, and the like. Moreover, the thing which carbon, titanium, silver was processed on the surface of copper, aluminum, and stainless steel, and the thing which oxidized these materials are used. In particular, aluminum and stainless steel are preferable in terms of cost. The shape is a film, a sheet, a net, a punched product, a lath body, a porous body, a foamed body, a molded body of a fiber group, etc. in addition to a foil. The thickness is 1 μm to 1 mm, but is not particularly limited.
[0058]
For the negative electrode, lithium, a lithium alloy or / and a substance capable of inserting and extracting lithium are used. For example, lithium metals, lithium / aluminum alloys, lithium / tin alloys, lithium / lead alloys, wood alloys and other lithium alloys, and materials that can be electrochemically doped / undoped with lithium, such as conductive polymers (polyacetylene, polythiophene) , Polyparaphenylene, etc.), pyrolytic carbon, pyrolytic carbon gas-phase pyrolyzed in the presence of a catalyst, carbon calcined from pitch, coke, tar, etc., and lithium ion intercalation / deintercalation Available graphite (natural graphite, artificial graphite, expanded graphite, etc.), inorganic compounds that can be doped / undoped with lithium ions (WO ₂ , MoO ₂ Etc.) or a complex thereof.
[0059]
Among these negative electrode active materials, pyrolytic carbon, pyrolytic carbon pyrolyzed in the gas phase in the presence of a catalyst, carbon fired from pitch, coke, tar, etc., carbon fired from a polymer, graphite (natural graphite) , Artificial graphite, expanded graphite, and the like) can be produced in the battery characteristics, particularly in terms of safety.
[0060]
In the case of using a conductive polymer, carbon, graphite, an inorganic compound, or the like as the negative electrode active material, a conductive material and a binder may be added. As the conductive material, carbon such as carbon black, acetylene black, and ketjen black, graphite powder (natural graphite, artificial graphite), metal powder, metal fiber, and the like can be used, but are not limited thereto. As the binder, fluorine-based polymers such as polytetrafluoroethylene and polyvinylidene fluoride, polyolefin-based polymers such as polyethylene, polypropylene, ethylene-propylene-diene-terpolymer, and styrene-butadiene rubber can be used. It is not limited.
[0061]
As the ion conductor, for example, an organic electrolyte, a solid electrolyte (polymer solid electrolyte, inorganic solid electrolyte), a molten salt, or the like can be used, and among these, an organic electrolyte can be preferably used. The organic electrolytic solution is composed of an organic solvent and an electrolyte. Organic solvents such as aprotic organic solvents such as propylene carbonate, methyl ethyl carbonate, and γ-butyrolactone, substituted tetrahydrofuran such as tetrahydrofuran and 2-methyltetrahydrofuran, dioxolane, diethyl ether, dimethoxyethane, diethoxyethane, methoxyethoxy Examples include ethers such as ethane, dimethyl sulfoxide, sulfolane, acetonitrile, methyl formate, and methyl acetate. Among these, 1 type or 2 or more types are mixed and used.
[0062]
Examples of the electrolyte include lithium salts such as lithium perchlorate, lithium borofluoride, lithium phosphofluoride, lithium hexafluoroarsenide, lithium trifluoromethanesulfonate, lithium halide, and lithium chloroaluminate. Or 2 or more types are mixed and used. An electrolytic solution is prepared by dissolving the electrolyte in the solvent selected above. The solvent and electrolyte used in preparing the electrolytic solution are not limited to those listed above.
[0063]
Known inorganic solid electrolytes include lithium nitrides, halides, oxyacid salts, and the like. For example, Li _Three N, LiI, Li _Three N-LiI-LiOH, Li _Four SiO _Four , Li _Four SiO _Four -LiI-LiOH, Li _Three PO _Four -Li _Four SiO _Four , Phosphorus sulfide compounds, Li ₂ SiS _Three Etc.
[0064]
Examples of the organic solid electrolyte include a substance composed of a polymer that dissociates the electrolyte and the electrolyte, and a substance that has an ion dissociation group in the polymer. Examples of the polymer that dissociates the electrolyte include a polyethylene oxide derivative or a polymer containing the derivative, a polypropylene oxide derivative or a polymer containing the derivative, and a phosphate ester polymer. In addition, there is a polymer matrix material containing the above aprotic polar solvent, a mixture of a polymer containing an ion dissociation group and the above aprotic electrolyte, or polyacrylonitrile added to the electrolyte. In addition, an inorganic solid electrolyte and an organic solid electrolyte can be used in combination.
[0065]
Examples of the separator for holding the electrolytic solution include nonwoven fabrics such as electrically insulating synthetic resin fibers, glass fibers and natural fibers, woven fabrics, micropore structure materials, and molded bodies such as alumina powder. Of these, non-woven fabrics such as synthetic resins such as polyethylene and polypropylene, and micropore structures are preferred from the standpoint of quality stability.
[0066]
Some of these synthetic resin nonwoven fabrics / micropore structures have a function in which the separator melts by heat and blocks between the positive electrode and the negative electrode when a battery malfunctions. These are also suitable from the viewpoint of safety. Can be used for The thickness of the separator is not particularly limited, but may be a thickness that can hold a necessary amount of the electrolyte and that prevents a short circuit between the positive electrode and the negative electrode. Usually, a thickness of about 0.01 mm to 1 mm, preferably about 0.02 mm to 0.05 mm can be used.
[0067]
The shape of the battery includes a coin type, a button type, a sheet type, a cylindrical type, a square type, and the like. In the case of a coin-type battery or a button-type battery, the electrode is formed in a pellet shape. In a cylindrical battery and a square battery, an electrode is mainly formed in a sheet shape, this electrode is put in a battery can, and the can and the electrode are electrically connected.
[0068]
The electrolytic solution is injected, and the opening of the battery can is sealed with a sealing plate through an insulating packing. Alternatively, the sealing plate and the can are insulated and sealed with a hermetic seal. At this time, a safety valve equipped with a safety element can be used as a sealing plate. For example, the safety element includes a fuse, a bimetal, a PTC element, etc. as an overcurrent prevention element. In addition to the safety valve, as a countermeasure against the increase in the internal pressure of the battery can, a method of making a crack in the gasket, a method of making a crack in the sealing plate, a method of making a cut in the battery can, and the like are used. Further, an external circuit incorporating an overcharge or overdischarge countermeasure may be used.
[0069]
The pellet-like or sheet-like electrode is preferably dried and dehydrated in advance. As a drying and dehydrating method, a general method can be used. For example, there is a method of using hot air, vacuum, infrared rays, far infrared rays, electron beams, low-humidity air or the like alone or in combination. The temperature is preferably in the range of 50 ° C to 380 ° C.
[0070]
Next, examples of the present invention and results of characteristic experiments using the same will be described together with comparative examples according to the prior art.
[0071]
<Examples 1-3>
Lithium acetate and acetic acid are each dissolved in water so that the molar ratio is 1: 1 to prepare a buffer solution. In this buffer solution, 0.03 mol of anhydrous lithium hydroxide and 0.03 mol of nickel acetate tetrahydrate are dissolved. Powdered oxalic acid is added to the aqueous solution and stirred at room temperature for 2 hours. The amount of succinic acid added is 0.045 mol.
[0072]
The precipitate formed in the coprecipitation reaction by addition of oxalic acid is filtered and dried. This precipitate is fired at 700 ° C. in an oxygen atmosphere for 10 hours, and the obtained fired product is pulverized. This is Example 1.
[0073]
The filtrate discharged when the precipitate is filtered is again used as a buffer solution to carry out a coprecipitation reaction. That is, 0.03 mol of lithium acetate and 0.03 mol of nickel acetate tetrahydrate are dissolved in this solution. To this is added 0.045 mol of powdered oxalic acid and stirred at room temperature for 2 hours. The produced precipitate is filtered and dried, and calcined under the same conditions as in Example 1. The obtained fired product is pulverized. This is Example 2.
[0074]
Further, following Example 2, the filtrate is used again as a buffer solution, and a fired product is obtained in the same manner. The fired product is pulverized. This is Example 3.
[0075]
LiNiO obtained as described above ₂ An electrode is produced using as an active material. LiNiO ₂ Then, acetylene black serving as a conductive material and polytetrafluoroethylene serving as a binder are mixed in a mortar at a ratio of 100: 10: 10. A titanium mesh is added to this mixture as a current collector, and pressure-molded to produce pellets having a diameter of 20 mm and a weight of 0.10 g. Current collection is performed by spot welding a titanium wire to a titanium mesh to obtain an electrode for evaluation.
[0076]
The electrode is evaluated by the triode method, and lithium is used for the counter electrode and the reference electrode. As the electrolytic solution, a solution obtained by dissolving lithium perchlorate at a ratio of 1 M in a solvent in which ethylene carbonate and ethyl methyl carbonate are mixed at a volume ratio of 1: 1 is used. The charge / discharge current density is 27.4 mA / g. First, constant current charge is performed up to 4.2 V with respect to lithium of the reference electrode, and then constant current discharge is performed up to 2.7 V. From the second time onward, charging and discharging were repeated in the same voltage range and the same current density. As a result, the first discharge capacities were 170 mAh / g, 173 mAh / g, and 175 mAh / g, respectively.
[0077]
Next, four examples of LiNiO according to the prior art ₂ LiNiO in line with the manufacturing method ₂ And LiNiO ₂ The result of having evaluated the electrode produced using was shown.
[0078]
<Comparative Example 1>
In this comparative example, LiNiO is a mixture of a lithium compound and a nickel compound that are both solid. ₂ It is a manufacturing method. Lithium hydroxide and nickel oxyhydroxide are weighed so that the molar ratio of lithium to nickel (lithium / nickel) is 1.1, and then mixed in a mortar. 100kg / cm to this mixture ² The pressure is applied to produce pellets. This is fired at 800 ° C. in an oxygen atmosphere for 2 hours. The obtained fired product is pulverized. This is referred to as Comparative Example 1.
[0079]
Production and evaluation of an electrode are performed according to the method of Examples 1-3 mentioned above. As a result, the first discharge capacity was 124 mAh / g.
[0080]
<Comparative example 2>
In this comparative example, LiNiO mixed with an aqueous lithium compound solution and an aqueous nickel compound solution is used. ₂ It is a manufacturing method. Lithium hydroxide and nickel chloride are weighed so that the molar ratio of lithium to nickel (lithium / nickel) is 1, and then dissolved in water to obtain an aqueous solution. While stirring the aqueous nickel chloride solution, the aqueous lithium hydroxide solution is gradually added and stirred at 30 ° C. for 5 hours. The mixed solution was dried at 90 ° C. to 100 ° C. and the obtained solid material was pulverized, and then 100 kg / cm. ² The pressure is applied to produce pellets. This is fired at 800 ° C. in an oxygen atmosphere for 2 hours. The obtained fired product is pulverized. This is referred to as Comparative Example 2.
[0081]
Production and evaluation of an electrode are performed according to the method of Examples 1-3 mentioned above. As a result, the first discharge capacity was 120 mAh / g.
[0082]
<Comparative Example 3>
This comparative example uses LiNiO to add water as a dispersion medium to a lithium compound and a nickel compound that are both solid. ₂ It is a manufacturing method. Lithium hydroxide and nickel hydroxide were weighed so that the molar ratio of lithium to nickel (lithium / nickel) was 1, and then a small amount of water was added as a dispersion medium and mixed in a mortar. This was dried at 90 ° C. to 100 ° C., and the obtained solid material was pulverized, and then 100 kg / cm ² The pressure is applied to produce pellets. This is fired at 800 ° C. in an oxygen atmosphere for 2 hours. The obtained fired product is pulverized. This is referred to as Comparative Example 3.
[0083]
Production and evaluation of an electrode are performed according to the method of Examples 1-3 mentioned above. As a result, the first discharge capacity was 110 mAh / g.
[0084]
<Comparative example 4>
In this comparative example, LiNiO in which an aqueous lithium compound solution is mixed with a solid nickel compound. ₂ It is a manufacturing method. Lithium chloride and nickel oxide are weighed so that the molar ratio of lithium to nickel (lithium / nickel) is 1, and then lithium chloride is dissolved in water to obtain an aqueous solution. A lithium chloride aqueous solution is gradually added to solid nickel oxide and kneaded at 30 ° C. for 5 hours. This was dried at 90 ° C. to 100 ° C., and the obtained solid material was pulverized, and then 100 kg / cm ² The pressure is applied to produce pellets. This is fired at 800 ° C. in an oxygen atmosphere for 2 hours. The obtained fired product is pulverized. This is referred to as Comparative Example 4.
[0085]
Production and evaluation of an electrode are performed according to the method of Examples 1-3 mentioned above. As a result, the first discharge capacity was 127 mAh / g.
[0086]
LiNiO of Examples 1-3 ₂ As a result of evaluating the performance of the electrode manufactured using the above, an initial discharge capacity of 170 mAh / g or higher is obtained. This value is the same as that of Comparative Examples 1 to 4. ₂ It is about 50 mAh / g or more higher than the electrode fabricated using
[0087]
Next, three buffer solutions used in Example 1 were prepared, and precipitates were obtained from each of these buffer solutions in the same manner as in Examples 1 to 3. The precipitate obtained from the first buffer solution is designated as sample 1. Similarly, the precipitates obtained from the second and third buffer solutions are designated as Sample 2 and Sample 3, respectively.
[0088]
The molar ratio of lithium to nickel (lithium / nickel) in the nine types of precipitates obtained was measured using ICP emission analysis. The lithium / nickel ratio in these precipitates is shown in Table 1.
[0089]
[Table 1]

[0090]
Further, these precipitates are fired. Then, electrodes were prepared using each fired product as an active material, and the electrodes were evaluated. The production and evaluation of the electrodes were performed in the same manner as in Examples 1 to 3. Table 2 shows the discharge capacity (mAh / g) in the first charge / discharge cycle.
[0091]
[Table 2]

[0092]
From the results in Tables 1 and 2, it is easy to control the lithium / nickel ratio in the precipitate by repeatedly using the filtrate discharged when the precipitate is filtered. Improves. In addition, this precipitate was calcined LiNiO. ₂ The initial electrode characteristics when using as an active material for the electrode are greatly improved.
[0093]
<Example 4>
Lithium acetate and acetic acid are each dissolved in water so that the molar ratio is 1: 1 to prepare a buffer solution. In this buffer solution, 0.03 mol of lithium hydroxide anhydride and 0.03 mol of nickel acetate tetrahydrate are dissolved. Powdered oxalic acid is added to the aqueous solution and stirred at room temperature for 2 hours. The amount of succinic acid added is 0.045 mol.
[0094]
The precipitate formed by the addition of oxalic acid is filtered. In the filtrate obtained during filtration vinegar Calcium acid is added to precipitate the oxalate ions present in the solution as calcium oxalate, and the precipitate is removed by filtration. Further, the excess acetic acid contained in the filtrate is separated by distillation, and a solution is prepared by taking into account the concentration of acetic acid and lithium ions, and 0.03 mol of lithium acetate and 0.03 mol of nickel acetate tetrahydrate are added to this solution. Dissolve. To this is added powdered oxalic acid and stirred at room temperature for 2 hours. The obtained precipitate is filtered and dried, and calcined at 700 ° C. in an oxygen atmosphere for 10 hours. The fired product is pulverized. This is Example 4.
[0095]
Production and evaluation of an electrode are performed according to the method of Examples 1-3 mentioned above. As a result, the first discharge capacity was 175 mAh / g.
[0096]
Next, three buffer solutions used in Example 4 were prepared, and precipitates were obtained from each of these buffer solutions in the same manner as in Example 4. The molar ratio of lithium and nickel in the three types of precipitates obtained was determined using ICP emission analysis. As a result, the lithium / nickel ratios in these precipitates were 1.05, 1.04, and 1.04, respectively.
[0097]
Further, the obtained precipitate is fired. Electrodes were produced using the fired products, and the electrodes were evaluated. The production and evaluation of the electrodes were performed in the same manner as in Examples 1 to 3. As a result, the first discharge capacity was 176 mAh / g, 176 mAh / g, and 175 mAh / g, respectively.
[0098]
From the above results, the LiNiO of Example 4 in which the solution was prepared so as to increase the accuracy of acetic acid and lithium ion concentration when the filtrate was repeatedly used. ₂ In this production method, variation in the lithium / nickel ratio in the resulting precipitate is reduced, and a more uniform precursor can be obtained. Moreover, LiNiO obtained by firing these precursors ₂ Is recognized as an active material that provides excellent initial electrode properties.
[0099]
<Examples 5 to 10 and Comparative Examples 5 to 7>
A buffer solution is prepared by dissolving lithium acetate and acetic acid in water so that the molar ratio is 1: 1. In this buffer solution, 0.3 mol of lithium hydroxide anhydride and 0.3 mol of nickel acetate tetrahydrate are dissolved. Powdered oxalic acid is added to the aqueous solution and stirred at room temperature for 2 hours. The amount of succinic acid added is 0.45 mol.
[0100]
After the precipitate formed by the addition of oxalic acid is filtered, 0.3 mol of lithium acetate and 0.3 mol of nickel acetate tetrahydrate are dissolved in the filtrate to prepare a solution. 0.45 mol of powdered oxalic acid is added to this aqueous solution and stirred at room temperature for 2 hours. The aqueous solution in which a precipitate is formed by the addition of succinic acid is filtered, and the resulting precipitate is dried. Here, the firing temperature and the fired product LiNiO ₂ In order to investigate the relationship with the performance of the electrode produced using the above, firing is performed at various temperatures.
[0101]
That is, the precipitate is baked at temperatures of 600 ° C., 650 ° C., 700 ° C., 750 ° C., 800 ° C., 850 ° C., 900 ° C., 940 ° C., and 980 ° C. The firing time is 5 hours. Both are fired in an oxygen atmosphere. These are referred to as Comparative Example 5, Examples 5 to 10, and Comparative Examples 6 and 7, respectively.
[0102]
LiNiO obtained by the above manufacturing method ₂ An electrode is produced using as an active material. At this time, LiNiO ₂ Other than mixing acetylene black to be a conductive material and polytetrafluoroethylene to be a binder at a ratio of 100: 8: 10, the procedure for preparing electrodes, the weight and size of pellets, etc. According to 3 of the electrode manufacturing method.
[0103]
Further, the electrodes of Examples 1 to 3 described above were used except that a solution obtained by dissolving lithium perchlorate at a ratio of 1M in a solvent in which ethylene carbonate and diethyl carbonate were mixed at a volume ratio of 1: 1 as an electrolytic solution was used. According to the evaluation method.
[0104]
FIG. 2 is a diagram showing the relationship between the firing temperature and the first discharge capacity. LiNiO is obtained by using the solution after filtering the precipitate to obtain the precipitate again and calcining it. ₂ It can be seen that good initial electrode characteristics can be provided even when manufactured. Moreover, if the firing temperature is 650 ° C. to 900 ° C., preferably 700 ° C. to 850 ° C., a high discharge capacity is obtained. Accordingly, the LiNiO according to the present invention is characterized in that the firing temperature is 650 ° C to 900 ° C. ₂ It was confirmed that an electrode having good initial electrode characteristics can be obtained by using this manufacturing method.
[0105]
<Examples 11 to 16, Comparative Examples 8 to 10>
A buffer solution is prepared by dissolving lithium acetate and acetic acid in water so that the molar ratio is 1: 1. In this buffer solution, 0.3 mol of lithium hydroxide anhydride, 0.24 mol of nickel acetate tetrahydrate and 0.06 mol of cobalt acetate are dissolved. Powdered oxalic acid is added to the aqueous solution and stirred at room temperature for 2 hours. The amount of succinic acid added is 0.45 mol.
[0106]
After the precipitate formed by the addition of oxalic acid is filtered, 0.3 mol of lithium acetate, 0.24 mol of nickel acetate and 0.06 mol of cobalt acetate are dissolved in the filtrate to prepare a solution. 0.45 mol of powdered oxalic acid is added to this aqueous solution and stirred at room temperature for 2 hours. The aqueous solution in which a precipitate is formed by the addition of succinic acid is filtered, and the resulting precipitate is dried. Here, the firing temperature and the fired product, LiNi _0.8 Co _0.2 O ₂ In order to investigate the relationship with the performance of the electrode produced using the above, firing is performed at various temperatures.
[0107]
That is, the precipitate is baked at temperatures of 600 ° C., 650 ° C., 700 ° C., 750 ° C., 800 ° C., 850 ° C., 900 ° C., 940 ° C., and 980 ° C. The firing time is 5 hours. Both are fired in an oxygen atmosphere. These are referred to as Comparative Example 8, Examples 11 to 16, and Comparative Examples 9 and 10, respectively.
[0108]
LiNi obtained by the above manufacturing method _0.8 Co _0.2 O ₂ An electrode is produced using as an active material. At this time, LiNi _0.8 Co _0.2 O ₂ Other than mixing acetylene black to be a conductive material and polytetrafluoroethylene to be a binder at a ratio of 100: 8: 10, the procedure for preparing electrodes, the weight and size of pellets, etc. According to 3 of the electrode manufacturing method.
[0109]
Further, the electrodes of Examples 1 to 3 described above were used except that a solution obtained by dissolving lithium perchlorate at a ratio of 1M in a solvent in which ethylene carbonate and diethyl carbonate were mixed at a volume ratio of 1: 1 as an electrolytic solution was used. According to the evaluation method.
[0110]
FIG. 3 is a diagram showing the relationship between the firing temperature and the first discharge capacity. LiNi is obtained by using the solution after filtering the precipitate to obtain the precipitate again and calcining it. _0.8 Co _0.2 O ₂ It can be seen that good initial electrode characteristics can be provided even when manufactured. Moreover, if the firing temperature is 650 ° C. to 900 ° C., preferably 700 ° C. to 850 ° C., a high discharge capacity is obtained. Therefore, the LiNi according to the present invention is characterized in that the firing temperature is 650 ° C. to 900 ° C. _0.8 Co _0.2 O ₂ It was confirmed that an electrode having a high initial discharge capacity can be obtained by using this manufacturing method.
[0111]
<Examples 17-22, Comparative Examples 11-18>
Lithium acetate and acetic acid are each dissolved in water in a molar ratio of 1: 1 so that the molar ratio is 1: 1 to prepare a buffer solution. In this buffer solution, 0.3 mol of lithium hydroxide anhydride and 0.3 mol of nickel acetate tetrahydrate are dissolved. Powdered oxalic acid is added to the aqueous solution and stirred at room temperature for 2 hours. The amount of succinic acid added is 0.45 mol.
[0112]
The precipitate formed by the addition of succinic acid is filtered and the resulting precipitate is dried. Here, the volume ratio of oxygen in the firing atmosphere and the generated LiNiO ₂ In order to investigate the relationship with the discharge capacity of the electrode manufactured using the above, firing is performed in atmospheres with various oxygen concentrations.
[0113]
That is, in a mixed gas of oxygen and nitrogen, the precipitate is fired in each atmosphere having an oxygen volume ratio of 10%, 20% (in air), 30%, 50%, 70%, 80%, and 100%. However, in any case, baking is performed at 700 ° C. for 8 hours. The obtained fired product is pulverized. Each of these cases is referred to as Comparative Examples 11-17.
[0114]
A solution obtained by filtering the precipitate is prepared in the same manner as in Example 4 described above, and then 0.3 mol of lithium acetate and 0.3 mol of nickel acetate are dissolved. To this, 0.45 mol of powdered oxalic acid is added and stirred at room temperature for 2 hours. The produced precipitate is filtered and dried, and calcined in the atmospheres having various oxygen concentrations described above.
[0115]
That is, the precipitate is fired in each atmosphere having an oxygen volume ratio of 10%, 20% (in air), 30%, 50%, 70%, 80%, and 100%. However, in any case, baking is performed at 700 ° C. for 8 hours. The obtained fired product is pulverized. Each at this time is referred to as Comparative Example 18 and Examples 17-22.
[0116]
The above LiNiO ₂ LiNiO obtained by the manufacturing method ₂ Is used as an active material to produce an electrode. At this time, LiNiO ₂ Other than mixing acetylene black to be a conductive material and polytetrafluoroethylene to be a binder in a ratio of 100: 15: 8, the procedure of electrode preparation, the weight and size of the pellet, etc. According to 3 of the electrode manufacturing method.
[0117]
In addition, the electrode evaluation of Examples 1 to 3 described above was used except that a solution in which propylene carbonate and dimethyl carbonate were mixed at a volume ratio of 1: 1 as an electrolytic solution and lithium phosphofluoride was dissolved at a ratio of 1 M was used. Follow the method.
[0118]
FIG. 4 is a diagram showing the relationship between the oxygen concentration in the firing atmosphere and the first discharge capacity. As shown in FIG. 4, the precipitate is obtained again using the solution after the precipitate is filtered, and is baked to produce LiNiO. ₂ It can be seen that good initial electrode characteristics can be provided even when manufactured. Further, when the oxygen concentration is 20% or more, preferably 50% or more, particularly 80% or more, a high discharge capacity is obtained. Therefore, the LiNiO according to the present invention is characterized in that the volume ratio of oxygen in the firing atmosphere is 20% or more. ₂ It was confirmed that an electrode having good initial electrode characteristics can be obtained by using this manufacturing method.
[0119]
<Example 23>
In this embodiment, LiNiO according to the present invention ₂ LiNiO manufactured by the manufacturing method of ₂ A simple battery is prepared using the positive electrode active material, and a charge / discharge test is performed. A positive electrode is produced according to the method for producing a positive electrode described in Example 2, and pellets having a diameter of 15 mm and a weight of 50 mg are obtained.
[0120]
The negative electrode active material includes pyrolytic carbon (plane distance (d002) between adjacent plane parallel to (002) plane: 0.337 nm, crystallite thickness in the (002) plane direction (Lc): 15 nm, argon laser Raman 1580cm of the scattering spectrum by the method ^-1 1360cm for nearby peak ^-1 The intensity ratio (R value) of the nearby peak is 0.45).
[0121]
Propane is used as a starting material, and it is subjected to atmospheric pressure gas phase pyrolysis at 750 ° C. for 2 hours. ² ) Is deposited on the substrate. A nickel wire was spot-welded to collect current and dried at 200 ° C. under reduced pressure to remove moisture to make a negative electrode (weight 35 mg).
[0122]
An electrolyte solution in which lithium perchlorate is dissolved at a ratio of 1 M is put in a solvent in which propylene carbonate and diethyl carbonate are mixed at a volume ratio of 1: 1 in a beaker type cell, and the above-described positive electrode and negative electrode are immersed in this electrolyte solution.
[0123]
The charge / discharge test of this battery is performed as follows. Constant current charging was performed at 0.2 mA up to an upper limit voltage of 4.4 V, followed by constant current discharging up to 2.5 V at the same current. The same is done for the second and subsequent times. As a result, the discharge capacity at the first charge / discharge cycle was 7.9 mAh, and the discharge capacity at the 100th cycle was 7.1 mAh.
[0124]
<Example 24>
In this example, a charge / discharge test of a coin-type battery according to the present invention is performed. LiNiO described in Example 2 ₂ LiNiO obtained by the manufacturing method of ₂ Is used as an active material, and a positive electrode is produced into pellets having a diameter of 15 mm, a thickness of 0.75 mm, and a weight of 0.20 g.
[0125]
The method for producing the negative electrode is as follows. The negative electrode active material is made of natural gas from Madagascar (scale-like, particle size: 11 μm, surface distance between adjacent (002) plane (d002): 0.337 nm, crystallites in the (002) plane direction. Thickness (Lc): 27 nm, spread of crystal layer in the (002) plane direction (La): 17 nm, scattering spectrum 1580 cm by argon laser Raman method ^-1 1360cm for nearby peak ^-1 Near peak intensity ratio (R value): 0, specific surface area: 8 m ² / g).
[0126]
Natural graphite and polytetrafluoroethylene as a binder are mixed at a ratio of 10: 1. Nickel mesh is added to the mixture as a current collector and pressure-molded to produce pellets having a diameter of 15 mm, a thickness of 0.59 mm, and a weight of 0.1 g. The pellet is dried at 200 ° C. under reduced pressure to remove moisture.
[0127]
The configuration of a coin-type battery using these electrodes is as follows. FIG. 5 shows a cross section of a coin-type battery according to the present invention. Inside the low cylindrical positive electrode can 1, an insulating packing 8 is placed along the side surface. A positive electrode 3 integrated with the positive electrode current collector 2 is crimped to the center side of the insulating packing 8.
[0128]
At this time, the positive electrode current collector 2 is in contact with the bottom surface of the positive electrode can 1. On the positive electrode 3, a polypropylene nonwoven fabric separator 7 and a negative electrode 6 integrated with the negative electrode current collector 5 are arranged in close contact with each other in this order from the bottom to the top. The separator 7 is impregnated with an electrolytic solution in which lithium phosphofluoride is dissolved at a ratio of 1 M in a solvent in which ethylene carbonate and diethyl carbonate are mixed at a volume ratio of 1: 1.
[0129]
A negative electrode can 4 is stacked on the negative electrode 6, and the negative electrode can 4 and the positive electrode can 1 are sealed by caulking with an insulating packing 8 interposed therebetween. Thus, the negative electrode 6 is pressure-bonded to the negative electrode can 4, and in particular, the negative electrode current collector 5 is in contact with the inner surface of the negative electrode can 4.
[0130]
The charge / discharge test of the coin-type battery is performed as follows. The charge / discharge current is set to 1 mA. First, constant current charging is performed up to a charging upper limit voltage of 4.4 V, and then constant current discharging is performed up to a discharge lower limit voltage of 2.5 V. From the second time onward, charging and discharging are repeated in the same current and voltage range.
[0131]
As a result, the discharge capacity at the first charge / discharge cycle was 28.5 mAh, and the discharge capacity at the 100th cycle was 25.0 mAh.
[0132]
<Example 25>
In this example, a charge / discharge test of a cylindrical battery according to the present invention is performed. First, a sheet-like positive electrode is produced. LiNiO described in Example 2 ₂ The positive electrode active material LiNiO by the manufacturing method of ₂ Manufacturing.
[0133]
This LiNiO ₂ A method for manufacturing an electrode using the above as an active material is as follows. LiNiO ₂ Then, acetylene black as a conductive material and polyvinylidene fluoride as a binder are mixed in a ratio of 100: 7: 10. Here, N-methyl-2-pyrrolidone as a dispersant is added and further mixed to obtain a positive electrode paste.
[0134]
This positive electrode paste is applied to both sides of an aluminum foil (thickness 20 μm) serving as a current collector, dried, rolled and cut into strips. The weight of the active material per unit area in this positive electrode is 40 mg / cm. ² It became. Further, an aluminum tab serving as a positive electrode lead is attached to one end of the positive electrode by spot welding.
[0135]
Artificial graphite as negative electrode active material (particle size: 8 μm, spacing between parallel surfaces of (002) plane (d002): 0.337 nm, thickness of crystal layer in (002) plane direction (Lc): 25 nm , Crystal layer spread in the (002) plane direction (La): 13 nm, wave number of scattering spectrum by argon laser Raman method is 1580 cm ^-1 1360cm for nearby peak ^-1 Near peak intensity ratio (R value): 0, specific surface area: 12 m ² / g). This artificial graphite and polyvinylidene fluoride used as a binder are mixed at a ratio of 100: 10.
[0136]
N-methyl-2-pyrrolidone as a dispersant is added to this mixture and further mixed to obtain a negative electrode paste. The negative electrode paste is applied to both sides of a copper foil (thickness 18 μm) serving as a current collector, dried, rolled, and cut into strips. The weight per unit area of the active material in this negative electrode is 20 mg / cm. ² It became. Further, a nickel tab serving as a negative electrode lead is attached to one end of the negative electrode by spot welding.
[0137]
The configuration of the cylindrical battery using these electrodes is as follows. FIG. 6 shows a cross section of a cylindrical battery according to the present invention. In this figure, the positive electrode lid 11, the insulating packing 12, and the separator 14 are omitted from hatching showing a cross section. A polyethylene microporous separator 14 is sandwiched between each of the positive electrode 16 and the negative electrode 15. These are wound spirally from the end so as to face each other to form a cylindrical winding element.
[0138]
This cylindrical winding element is housed in a cylindrical battery can (diameter 17 mm, height 50 mm, made of stainless steel) with the positive electrode lead drawn from the upper surface and the negative electrode lead drawn from the lower surface. The positive electrode lead is attached to the positive electrode lid with a safety valve, and the negative electrode lead is attached to the bottom surface of the battery can by spot welding. In addition, a center pin 17 (diameter 3.4 mm, length 40 mm, stainless steel tube) is inserted in the center of the winding element to prevent collapse.
[0139]
As an electrolyte, an electrolytic solution in which lithium phosphofluoride is dissolved at a ratio of 1 M in a mixed solvent in which ethylene carbonate and diethyl carbonate are mixed at a volume ratio of 1: 1 is poured into a battery can. The positive electrode lid 11 and the battery can 13 are sealed by caulking with an insulating packing 12 interposed therebetween.
[0140]
The charge / discharge test of this cylindrical battery is performed as follows. In a constant temperature bath at 25 ° C., constant current and constant voltage charging with 500 mA and an upper limit voltage of 4.2 V were performed for 3 hours, and constant current discharge with 100 mA and a lower limit voltage of 2.75 V was performed. The same is done for the second and subsequent times. As a result, the discharge capacity at the first charge / discharge cycle was 918 mAh, and the discharge capacity at the 50th cycle was 805 mAh. Therefore, it was recognized that the non-aqueous secondary battery according to the present invention is a secondary battery in which the discharge capacity does not decrease even during repeated charge and discharge.
[0141]
【The invention's effect】
As described above, a nickel compound and a lithium compound are used as raw materials, dissolved in a buffer solution, co-precipitated with oxalic acid, and the filtrate discharged when the precipitate is filtered is again used as a buffer solution. LiNiO according to the present invention, characterized in that it is used repeatedly to obtain a precursor. ₂ According to this production method, a more uniform precursor with less variation in the molar ratio of lithium to nickel (lithium / nickel) can be obtained.
[0142]
In addition, after separating the oxalate ions and acetic acid from the filtrate obtained by filtering the precipitate, by preparing a solution to increase the accuracy of the acetic acid and lithium ion concentration in the solution, the uniformity of the precursor is further improved. Stabilize.
[0143]
In addition, by re-preparing to the conditions before adding succinic acid, the filtrate was repeatedly used for LiNiO ₂ Therefore, it is not necessary to use a large amount of raw materials every time, so that costs can be reduced and resources can be used effectively.
[0144]
LiNiO obtained by firing this precursor ₂ In the non-aqueous secondary battery according to the present invention using as the active material for the electrode, a high initial discharge capacity can be obtained. Furthermore, in the secondary battery according to the present invention, the discharge capacity does not decrease so much even in repeated charge / discharge, so that the secondary battery has a long life.
[Brief description of the drawings]
FIG. 1 LiNiO according to the present invention ₂ Or LiNi _1-X M _X O ₂ It is a figure which showed the manufacturing method of (0 <X <0.5 and M is at least 1 sort (s) of element chosen from a transition metal, 3B group element, 4B group element, or 5B group element).
FIG. 2 is a graph showing the relationship between firing temperatures and initial discharge capacities in Examples 5 to 10 and Comparative Examples 5 to 7.
FIG. 3 is a graph showing a relationship between firing temperatures and initial discharge capacities of Examples 11 to 16 and Comparative Examples 8 to 10.
4 is a graph showing the relationship between the oxygen concentration in the firing atmosphere and the initial discharge capacity in Examples 17 to 22 and Comparative Examples 11 to 18. FIG.
FIG. 5 is a cross-sectional view of a coin-type battery according to the present invention.
FIG. 6 is a cross-sectional view of a cylindrical battery according to the present invention.
[Explanation of symbols]
1 Positive electrode can
2 Positive current collector
3 Positive electrode
4 Negative electrode can
5 Negative electrode current collector
6 Negative electrode
7 Separator
8 Insulation packing
11 Positive cover
12 Insulation packing
13 Battery can
14 Separator
15 Negative electrode
16 Positive electrode
17 Center pin

Claims (4)

A step of buffer solution consisting of acetic acid and lithium acetate to dissolve the lithium acetate or lithium hydroxide and nickel acetate to prepare a solution, adding an oxalic acid in aqueous solution, from the solution after addition of the oxalic acid The method comprises a step of separating a precipitate and a step of firing the precipitate obtained in the filtration step, and after separating and removing oxalate ions and acetic acid from the filtrate obtained in the filtration step, the oxalic acid A method for producing a positive electrode active material for a non-aqueous secondary battery comprising LiNiO ₂ , wherein the filtrate is repeatedly used by re-preparing to the conditions before addition of. By dissolving a compound containing at least one element selected from the buffer solution lithium acetate or lithium acetate nickel hydroxide and a transition metal or a Group 3B element or Group 4B elements or Group 5B elements consisting of acetic acid and lithium acetate A step of preparing an aqueous solution, a step of adding succinic acid to the aqueous solution, a step of filtering a precipitate from the solution after addition of the succinic acid, and a step of baking the precipitate obtained by the filtering step LiNi ₁ characterized in that, after separating and removing oxalate ions and acetic acid from the filtrate obtained in the filtration step, the filtrate is repeatedly used by re-preparing to the conditions before adding the oxalic acid. _{-X M X O 2 (0 <} X <0.5, M is at least one element selected from transition metals or a group 3B element or group 4B elements or group 5B elements) positive active for a nonaqueous secondary battery comprising Method of manufacturing quality. The method for removing the oxalate ion is performed using calcium acetate, or the positive electrode active material for a non-aqueous secondary battery or LiNi _1-X M _X containing LiNiO _{2 according} to claim 1 or 2. A method for producing a positive electrode active material for a non-aqueous secondary battery containing O ₂ (0 <X <0.5, M is at least one element selected from a transition metal, a group 3B element, a group 4B element, or a group 5B element). The firing process the firing temperature is 650 ° C. or higher 900 ° C. or less, the firing atmosphere is one of claims 1 to 3, characterized in that the volume rate of air or oxygen is carried out in an atmosphere of 100% less than 21% LiNiO ₂ -containing positive electrode active material or LiNi _1-X M _X O ₂ (0 <X <0.5, where M is a transition metal, a group 3B element, a group 4B element or a group 5B element A method for producing a positive electrode active material for a non-aqueous secondary battery comprising at least one selected element).

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